Ancient Calendar

The Ancient, Julian, & Gregorian Calendar, and Names of the Days of the Week

Fasti. Courtesy of Wikipedia.
"Be quiet! The Roman calendar is the most perfect yet devised. It has twelve months."
"Except when it has thirteen, as this year."
"And all of these months have either thirty-one or twenty-nine days."
"Except Februarius, which has twenty-eight. Only this year, according to you, it has only twenty-four."

~ Steven Saylor Murder on the Appian Way, p. 191.

Early farmers couldn't simply look at a wall calendar to see how many days until the last frost date. However, knowing there were approximately 12 moon cycles between one spring and the next, they could calculate how many lunar phases remained before planting season. Thus was born the concept of the 354 day lunar calendar, a concept eternally at odds with the approximately 365.25 day solar year.

Blending time derived from the motions of the rotating earth, the earth revolving around the sun, and the moon's passage as the earth's satellite is hard enough, but the Mayans had 17 cosmological calendars, some of which go back ten million years and require the services of astronomers, astrologers, geologists, and mathematicians to figure out. Introduction to Mayan Calendar Terminology provides simplified information on some of the cycles and glyphs used in the Mayan calendars.
~ From Mayan Calendar Terminology (1)

The position the planets is vital to many calendars. At least once, on March 5, 1953 B.C.-- at the beginning of Chinese calendar time -- all the planets, the sun and the moon were in alignment.
~ Source (2)

Even our calendar system calls on this relationship with the planets. Names for the days of the week (although the Teutonic Woden, Tiw, Thor, and Frigg have replaced the Roman names for deities of related prowess) refer to various celestial bodies. Our 7-day week began under Augustus. [See table below.]

According to "Calendars and Their History," calendars permit us to plan our farming, hunting, and migrating activities. They may also be used for prediction and to establish dates for religious and civic events. However accurate we might try to make them, calendars should be judged not by their scientific sophistication, but by how well they serve social needs.
~ From Calendars and Their History (3)

Calendar Reform disagrees. Its author thinks it's high time for reform. Our Gregorian calendar, adopted in 1751 by an act of Parliament, uses basically the same months Julius Caesar established 2 millennia ago, in 45 B.C.
~ From Calendar Reform (4)

Julian Calendar Reform

Caesar faced an unreliable lunar calendar system based on a distrust of even numbers. The original first month, Martius, had 31 days, as did Maius, Quinctilis (later renamed Julius), October, and December. All the other months had 29 days, except the last month of the year, which was allowed to be unlucky with only 28 days. (The Aztecs, too, considered certain days of their xihutl calendar to be unlucky.) Finding, over time, that their calendar didn't correspond with the seasons of the solar year, the Romans, like the Hebrews and Sumerians, intercalated an extra month -- whenever the College of Pontiffs deemed it necessary (as in the passage from Murder on the Appian Way).

Caesar turned to Egypt for guidance with the difficult Roman calendar. The Ancient Egyptians predicted the annual Nile flooding on the basis of the appearance of the star Sirius. The period between was 365.25 days -- less than an hour wrong in five years. So, abandoning the Roman lunar calendar, Caesar set alternating months of 31 and 30 days with February having only 29 days except every fourth year when February 23 was repeated.
~ Source (5)

Why the 23d? Because the Romans didn't yet count from the beginning of the month, but from before it. They counted how many days before the Nones, Ides, and Kalends of each month. February 23 was counted as six days before the kalends of March -- the old beginning of the year. When it was repeated, it was referred to as bi-sextile.

What Was the Format of the Roman Fasti Calendar?

Gregorian Calendar Reform

Pope Gregory XIII's major changes were algorithms to calculate movable feasts and a new system of leap years that got rid of leap years in years that are divisible by 100 but not 400. Pope Gregory also deleted ten days from the 1592 calendar year in order to accommodate a shift in the equinox.

When Did We Switch From the Roman Fasti Calendar to the Modern?

A variety of calendars culminate around the year 2000. Calendar Convergence shows the common end of calendar cycles from the Hopi, the Ancient Greeks, the Early Egyptian Christians, the Mayan, and the Indian Vedic tradition. Planets Alignments in 2000 shows an alignment of the seven planets on May 5, 2000.
~ From Calendar Convergence (6) and Planets Alignments (7)

U. Glessmer. "The Otot-Texts (4Q319) and the Problem of Intercalations in the Context of the 364-Day Calendar" in:
Qumranstudien: Vortraege und Beitraege der Teilnehmer des Qumranseminars auf dem internationalen Treffen der Society of Biblical Lit., Muenster, 25-26. Juli 1993 [Hans-Peter Mueller zum 60. Geburtstag]. Schriften des Institutum Judaicum Delitzschianum; Bd. 4. Ed. H.J. Fabry et al. Goettingen 1996, 125-164.
~ From ANE discussion (8)


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Table of the Days of the Week

dies Solis Sun day Sunday domenica (Italian)
dies Lunae Moon day Monday lunedì
dies Martis Mars's day Tiw's day Tuesday martedì
dies Mercurii Mercury's day Woden's day Wednesday mercoledì
dies Jovis Jupiter's day Thor's Day Thursday giovedì
dies Veneris Venus's day Frigg's day Friday venerdì
dies Saturni Saturn's day Saturday sabato

 Related ResourcesJulius Caesar
• Maya Calendar Round
• Intercalation
• Gregorian Calendar
• Julian Calendar

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Your Citation
Gill, N.S. "Ancient Calendar." ThoughtCo, Feb. 16, 2021, Gill, N.S. (2021, February 16). Ancient Calendar. Retrieved from Gill, N.S. "Ancient Calendar." ThoughtCo. (accessed March 24, 2023).